machine learning human 7 Article 6 Humans 6 adult 4 female 4 male 4 mathematical model 4 signal noise ratio 4 Learning systems 3 Machine-learning 3 electrocardiography 3 human experiment 3 learning algorithm 3 nerve cell network 3 physical activity 3 random forest 3 support vector machine 3 Classification (of information) 2 Decision trees 2 Electrocardiography 2 Learning algorithms 2 Machine learning 2 Support vector machines 2 Support vector regression 2 Walking 2 Wearable Electronic Devices 2 Wearable sensors 2 Wrist 2 accuracy 2